[GRASS-user] TOPOGRID equivalent in GRASS?

[Maciej Sieczka]

Dylan Beaudette wrote:
> Hi Jonathan,
> 
> If I am not mistaken, TOPOGRID is just a front end to the well-known
> interpolation algorithm used in Anudem
> (http://cres.anu.edu.au/outputs/anudem.php).

Mind that TOPOGRID is based on Anudem version few years old now, and
has not been updated since then, while Anudem has gained new
functionalities and fixes in the meantime.

> To my knowlegde, and based on past mail-list traffic, GRASS does not
> have an algorithm like this. You can approach this type of
> functionality with v.surf.nbathy

Typo notice: that's r.surf.nnbathy ;).

> / v.suf.rst / etc, along with r.carve
> to 'burn-in' the stream lines. Maciek has looked into this, and
> contributed much discussion on the list.
> 
> There has been some recent traffic on some new scripts (v.???) built
> by Maciek -- which incorporate stream lines (?) ..

Dylan means v.breach. It is similar to r.carve. The main difference is
that it honours the streamline's direction, like Anudem, while r.carve
does not. Also, it does not output the breached DEM itself, but only
the "breached" elevation vector points along intput streamlines, one
point per one DEM cell. These points can be burned into DEM with
v.to.rast=r.mapcalc later or used as an aid in interpolating more
hydrologically sound DEM with your fave method.

Maciek